[Paraview] Reader Plugin Dev: "NA" extents & how to print debug messages?

[Peter Schmitt]

Hi ParaViewers,

(Sorry if this double-posts!)

I am writing a ParaView Reader Plugin to get my data into ParaView via a
vtkStructuredGrid object.  I can load my plugin into ParaView via "Manage
Plugins".  My file type shows up in the "File-> Open" dialog.  When
PV_PLUGIN_DEBUG is set, the "Output Messages" window shows that the library
was loaded successfully.

When I select a file and click "Apply" in the object inspector, Paraview
thinks for a split second before returning to an interactive state.
 However, no data appears & the "Information" tab of the object inspector
sets nCells = 0; nPoints = 0; Memory = 0 MB and the X,Y,Z extents are "NA".

My plugin reader derives from "vtkStructuredGridReader" and implements:

* SetFileName
* GetFileName
* CanReadFile
* RequestInformation, where I set the extents via:
  outInfo->Set(vtkStreamingDemandDrivenPipeline::WHOLE_EXTENT(),extent,6);
* RequestData, where I obtain a vtkStructuredGrid via:
  vtkStructuredGrid *output =

 vtkStructuredGrid::SafeDownCast(outInfo->Get(vtkDataObject::DATA_OBJECT()));

I am not sure why the "Information" tab is showing an empty structured grid.
 My questions are:

1.  How can I print debugging messages to stdout or Paraview's own "Output
Messages" window?  Specifically, I'd like to make sure that my X,Y,Z extents
are being read properly from file.   I tried vtkDebugMacro, but the data
isn't being printed.

2.  Have I implemented the appropriate functions that derive from
vtkStructuredGridReader?

3.  Should I derive instead from another class?  When I derive from
vtkStructuredGridAlgorithm, I get three error messages from
vtkCompositeDataPipeline:  "Input port 0 of algorithm
vtkLFMReader(0x11f98a720) has 0 connections but is not optional".

Can you offer any hints of how I can proceed to debug my reader?

Thanks!
Pete
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